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Dr Bill Durodié

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Toxic salmon? Codswallop
A BBC documentary on the potential dangers of farmed salmon made for big publicity - but contained little evidence.

Salmon recently got the BBC into hot water - not Peter Salmon, former controller of BBC1, but the programme The Price of Salmon - screened by BBC2 on 7 January as part of its series 'Warnings from the Wild'.

The high-profile documentary suggested that wild salmon may be becoming extinct. In the week preceding the programme, this issue was the subject of a radio debate on BBC Radio 4's flagship news programme Today, and spawned a rash of newspaper articles with titles such as 'Salmon poison alert' and 'King of fish contaminated by chemicals'.

But not all publicity was good publicity. The Price of Salmon also attracted accusations of scaremongering from the recently established Food Standards Agency (FSA). And so it should have.

In essence, Julian Pettifer, the programme's writer and presenter, claimed that farmed salmon are leading to the depletion of natural stocks as well as potentially damaging our health. To press the message home, exaltation of the 'beauty', 'power', 'grace' and 'endurance' of salmon was contrasted to an 'intensive' 'industry' run by 'multinationals' and 'politicians' who have failed to learn the lessons of GM or BSE.

Never mind that, unlike cattle, salmon are natural carnivores, or that salmon returned to the River Thames in 1974 after a break of almost 150 years. In the programme's efforts to convince, everything was thrown into the pot. When they were not spreading sea-lice or being victims of 'stress', farmed salmon were disturbing natural habitats or even escaping.

More significantly, we were informed that farmed salmon now contain high levels of potentially dangerous pollutants. This would seem to be yet more bad news for hungry consumers: partly due to the spate of scare stories surrounding meat from farm animals, salmon has become one of our more popular dishes over the past decade. The industry as a whole has become the world's fastest growing food sector. Accusations of toxicity would not just harm producers concentrated in the highlands and islands of Scotland, Norway and Canada, but further erode consumer confidence in scientists and politicians.

There may be many reasons why numbers of wild salmon appear to be in decline, such as problems relating to their freshwater habitats, rising seal populations in the absence of culls, or the fishing of their natural prey to feed the farmed variety. But these were not explored by the BBC's programme.

Much of the research cited in the programme remains unpublished and hence unverifiable. One such piece, sponsored by the David Suzuki Foundation, a Canadian environmentalist group keen on religious metaphors and which has such scientific luminaries as Body Shop founder Anita Roddick and rock star Sting on its board of directors, admits to being based on 'a small sample size'. An independent study by Miriam Jacobs, a part-time lecturer studying for a PhD at the University of Surrey, was cited as corroborating evidence. Her research consisted of tests on a total of 12 fish.

The programme's researchers claimed to have discovered that farmed salmon, which now constitute some 98 percent of all the salmon we consume, contain levels of 'toxic' chemicals up to 10 times greater than the levels found among their wild cousins. It was held that these pollutants originate from the concentrated protein pellets fed to the salmon.

The pellets, made in part from fish the salmon would usually eat, were purported to have high levels of such chemicals, although why this should be is far from evident, and intriguingly these levels were less than in the salmon themselves. The specific chemicals 'causing concern' are polychlorinated biphenyls (PCBs), dioxins and other organochlorine compounds.

But should these chemicals really be 'a cause for concern'? It is true that tests on laboratory animals at very high doses suggest that these chemicals disrupt the nervous and immune systems, as well as impairing development and possibly affecting fertility. But there is a vast gulf between these chemicals' potential for harm, and the reality.

Even in the worst instances, such as the explosion at a chemical plant in Seveso, Italy in 1976, nobody has ever been exposed to harmfully high doses for prolonged periods. The most potent dioxin, 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD), shot to public prominence as a result of the Seveso accident - yet the only abnormal finding detected to date among those exposed has been a form of acne. Nevertheless, in order to attract research funding, its impact was overstated and this dioxin became known as 'the most toxic man-made chemical known'.

The first rule of toxicology is that all chemicals produce an effect, but it is the dose that makes the poison. The fact that a substance contains a toxin does not make it poisonous, otherwise all food, which invariably contains salt, a know toxin at high doses, would have to be banned. Nevertheless, resorting to the lowest common denominator of many such debates, the BBC programme repeated the cry, 'What about the children?'. A cursory look at the programme's message board on the BBC website, in response to the programme, showed that viewers had been most affected by the fear that salmon might harm their children.

Great import was attached to the recent downward revisions of tolerable daily intake (TDI) doses for such pollutants by the World Health Organisation (WHO) and the European Commission (EC). But environmental levels of PCBs, now banned but once widely used as liquid coolants, lubricants and insulators on industrial equipment, and TCDD and other dioxins, products of many combustion processes including burning wood, have fallen steadily over the past 20 years.

But back in 1982 the dietary intake of these toxins invariably exceeded the new TDI by up to 10 times. The good news is that only the worst measured levels today marginally exceed this dose, and as an average this would have to be consistently repeated to breach the new recommendations. In other words, you would be sick of salmon well before being made sick by it. If there remains a problem for children, then presumably there is a whole cohort from the early 1980s who are irreparably damaged and who can now serve as a source for much further experimentation.

Understanding that man does not live by salmon alone, the FSA continues to adhere to the notion that in a proper risk analysis of the situation, the benefits vastly outweigh the risks. Eating fish is considered to be good for health and forms part of a balanced diet having a beneficial impact upon coronary problems and arthritis. Little wonder that Eskimos and the Japanese seem to suffer less from these modern blights than all other cultures.

It is also worth indicating that the concerns that led to the WHO slashing exposure limits by 90 percent centred primarily upon these substances' purported actions as endocrine-disrupting chemicals (EDCs), rather than their high-dose carcinogenicity, which has been disputed by the US National Academy of Science.

EDCs are known by the media as 'gender-benders' and are chemicals that are held to affect our hormonal balance. Many of these are natural and found in food at doses millions of times greater than those to which we are exposed by synthetic compounds. Their action upon humans is widely disputed, as recognised by the EC in its own study, published in 2000, which showed no evidence for such effects. Nonetheless, EDCs then became regulated by the new WHO guidelines.

Since The Price of Salmon was screened, Miriam Jacobs, who undertook her research with the US Environmental Protection Agency (EPA), has indicated that her findings have been misinterpreted and has requested an apology from the BBC. The FSA are considering writing a formal letter of complaint. The evident nervousness and defensiveness of FSA officials on the programme, however, is unlikely to help improve the reputation of its chairman, Sir John Krebs - who has been previously accused of 'still giving advice like a scientist instead of a consumer health watchdog'.

It seems you can set up new 'independent' bodies in the age of consumer risk - but God forbid that they become too independent.

Published on Spiked, 22 January 2001